AsyncSSH AuthorizedKeysFile %u path traversal allows attacker-selected authorized keys to authenticate a traversal username

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.9 · CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P · score source

EPSS

• CVE-2026-45309: 0.59% estimated exploitation activity in the next 30 days; percentile 48.35 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary AsyncSSH 2.22.0 expands the OpenSSH-compatible AuthorizedKeysFile %u token with the raw SSH username during pre-authentication server config reload. A server configured with a documented per-user key pattern such as AuthorizedKeysFile authorizedkeys/%u can be made to read an authorized-keys file outside the intended directory when the SSH username contains path traversal segments. If the attacker can place or reference a readable authorized-keys-format file containing their public key, the attacker can authenticate over SSH as the traversal username. Affected Product - Package: asyncssh - Ecosystem: pip - Affected versions: confirmed on 2.22.0; exact lower bound not finalized - Tested version: 2.22.0 - Audit commit/tag: tag v2.22.0, commit af5a81e669633d83d535163f93b6bf3f957c9238 - PyPI sdist SHA256: c3ce72b01be4f97b40e62844dd384227e5ff5a401a3793007c42f86a5c8eb537 Vulnerability Details - CWE: CWE-22: Improper Limitation of a Pathname to a Restricted Directory - Component:…

Published by the source

27 May 2026, 21:35 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 13:41 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-g794-3fmp-753h

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-g794-3fmp-753h

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# Patch Next advisory brief: CVE-2026-45309

Advisory: AsyncSSH `AuthorizedKeysFile %u` path traversal allows attacker-selected authorized keys to authenticate a traversal username
IDs: CVE-2026-45309, GHSA-g794-3fmp-753h
Record: https://patchnext.com/advisories/cve-2026-45309 (revision 3, source checked 26 Oct 2026, 13:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: asyncssh 2.23.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI asyncssh: affected >= 2.22.0, <= 2.22.0; fixed in 2.23.0

## Suggested inspection (read-only)
- `python -m pip show asyncssh`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on asyncssh.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-g794-3fmp-753h (OSV record GHSA-g794-3fmp-753h lists affected ranges: PyPI asyncssh >=2.22.0 <2.23.0 (fixed))
- Verified: https://github.com/advisories/GHSA-g794-3fmp-753h (GitHub-reviewed advisory GHSA-g794-3fmp-753h lists affected ranges: PyPI asyncssh >=2.22.0 <=2.22.0)

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